Articles are often formed by injecting heated fluid into molds. The fluid is introduced into a runner in a nozzle body. The fluid then flows through passages in the nozzle body and through a gate well into a hollow cavity in the mold. The fluid is heated as it flows through the passages. When the fluid has solidified in the hollow cavity in the mold, it is sheared at the position where the fluid flows through the gate well into the hollow cavities in the molds.
Articles have been formed for decades, if not centuries, by injecting fluid into hollow cavities in molds. In all of this period of time, certain problems have continued to exist in spite of considerable efforts during this period to resolve such problems. For example, at the position where the fluid flows from the gate well in the nozzle body into the hollow cavity in the mold, a scar is formed in the smooth periphery of the article when the article is sheared at the gate well after the article has solidified.
There are other unresolved difficulties in the injection molding of articles. For example, it has been difficult to simultaneously form a plurality of articles satisfactorily from fluid flowing through a plurality of passages in a single nozzle body. It has also been difficult to form articles of a first particular color with a minimal effort in a mold immediately, or even shortly, after articles of a second color have been previously formed in the mold. The fluid remaining in the nozzle body with the second color tends to contaminate the fluid of the first color for an extended period of time after the fluid of the first color has been introduced into the storage body.
This invention provides apparatus which resolves satisfactorily the problems discussed in the previous paragraphs. For example, a single nozzle body is able to inject fluid simultaneously into a plurality of mold cavities to obtain the simultaneous formation of articles in the mold cavities. The single nozzle body also provides for the formation of articles which have a smooth peripheral surface at the positions of the shear when the articles are sheared from the gate well in the nozzle body after they have solidified in the mold. The apparatus of this invention is also advantageous in that an article of a first color can be produced without color contamination by the passage of fluid of that color through the nozzle body shortly after a fluid of a different color has previously passed through the nozzle body.